Comparative Analysis on Chemical Components and Antioxidant Activity for Different Aged Kang Bricks Teas
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Abstract:
Five aged Kang brick teas were used as analytical materials to comparatively analyze its tea polyphenols, catechins and tea pigments. EC50 analysis of antioxidant activities were determined of FRAP, DPPH· and ABTS·. The results showed that contents of the components increased significantly (p<0.05), including catechins, gallic acid, theabrownin and flavonoids during storage period. The median effect concentration (EC50) of FRAP reached from eight point twenty-eight μg/mL to fourteen point fifty-five μg/mL, which were higher than that of DPPH· (4.26 μg/mL~4.99 μg/mL) and ABTS· (5.14 μg/mL~5.50 μg/mL) (p<0.05). EC50 of DPPH· was lower than that of ABTS· (p<0.05). With the prolongation of storage period, DPPH·EC50 decreased significantly, and FRAP EC50 increased and next decreased significantly. ABTS·EC50 was significantly lower than other samples in storage period of 6 years. The ability of reducing iron ion and scavenging DPPH· radical of the extracts stored for 15 years and 22 years was significantly higher than that of other years. The correlation analysis showed that EC50 of FRAP and EC50 of DPPH were negatively correlated with gallic acid and theanine (p<0.05), and the EC50 of ABTS was positively correlated with gallic acid (p<0.05). Therefore, the polyphenol extract of Kang bricks tea has antioxidant activity. The longer the storage time is, the stronger the ability of reducing and scavenging DPPH· radical are, but there is no obvious relavance between the ability of removing ABTS and the storage time.
